Variable-focus lens system

摘要

A variable-focus lens system includes a negative front lens group, and a positive rear lens group. The focal length of the variable-focus lens system is varied by changing the distance between the front and said rear lens groups. The lens system satisfies the following conditions:whereinfx designates the focal length of the front lens group, which is less than zero;fy designates the focal length of the rear lens group, which is greater than zero; andFw designates the focal length of the entire variable-focus lens system at the short focal length extremity.